Filmstrip projectors with synchronized sound recording are widely used for various purposes including training and sales promotion. Such projectors utilize a magnetic tape recording which is played in a synchronized manner with the advancement of the filmstrip. One well-known projector of this type is sold under the trademark "Filmosound 35" as Model 756 by the Bell & Howell Company of Chicago, Ill. This projector uses a 35 millimeter filmstrip and a standard magnetic tape cassette in a single cartridge to facilitate handling and the loading of the projector.
To prepare the cartridge for use in the projector, the cartridge is loaded with a filmstrip and with a companion magnetic tape cassette. Typically, this preparation in the first instance, is done by the producer of the audiovisual materials. It is not uncommon for a producer to supply loaded cartridges in large numbers so that the loading is done on a production-line basis. In use of a cartridge with a projector, in case of audio-recording on both tape tracks for the same filmstrip, the user will be required to remove and reload the cassette into the cartridge. In the interest of time, it is highly desirable to be able to load and remove the tape cassette from the cartridge.
A cartridge of the type referred to above is disclosed in U.S. Pat. No. 3,799,420. In this cartridge, a base including a mounting plate supports a filmstrip housing on the upper side, i.e. at the top of the cartridge. On the bottom of the cartridge the mounting plate is provided with downwardly extending end flanges forming a channel which receives the tape cassette. The tape cassette is secured in place by means of an elongated retaining spring which extends from one flange across the full length of the cassette to the other flange. This arrangement for securing the cassette in the cartridge has the disadvantage that the spring is awkward to manipulate and the loading of the tape cassette is a time-consuming operation. Additionally, the retaining spring is a separate piece of the cartridge requiring assembly by the cartridge manufacturer and it also constitutes a relatively costly part of the cartridge.
A general object of this invention is to provide an improved cassette retaining means for such a cartridge and to overcome the above noted disadvantages.